Activated partial thromboplastin time predicts mortality in patients with severe fever with thrombocytopenia syndrome: A multicenter study in north China.

Background: Severe fever with thrombocytopenia syndrome (SFTS) is an emerging infectious disease with high lethality. This study aimed to determine whether prolonged activated partial thromboplastin time (APTT) predicted SFTS mortality. Methods: SFTS patients were enrolled from 6 hospitals in the north China. Subjects were divided into training cohort and 5 externally validation cohorts. The least absolute shrinkage and selection operator Cox regression model was performed to screen potential prognostic factors. Risk factors were analyzed using multivariable regression models. Prognostic models were established by Cox regression and random survival forest (RSF) methods, and evaluated regarding discrimination, validity and clinical benefit. Time-dependent receiver operating characteristic (ROC) curve was used to evaluate the predictive effectiveness of variables. Results: 1332 SFTS cases were included, in which 211 patients died. Six potential prognostic factors were screened, and pulse, breath, APTT and aspartic transaminase (AST) were independently associated with mortality in both training cohort (Yantai, N = 791) and external validation cohort (N = 541). APTT was steadily correlated with the fatality (HR: 1.039-1.144; all P < 0.01) in each five sub-validation cohorts (Dandong, Dalian, Tai'an, Qingdao and Beijing). RSF model with variables of APTT, AST, pulse and breath had considerable prognostic effectiveness, which APTT showed the highest prognostic ability with the area under the curve of 0.848 and 0.787 for 7-day and 14-day survival, respectively. Survival differences were found between high and low levels of APTT for mortality using 50s as the optimal cut-off. Conclusions: SFTS patients have prolonged APTT, which is an independent risk factor for fatality. APTT≥50s was recommended as a biomarker to remind physicians to monitor and treat patients more aggressively to improve clinical prognosis.

[Optimization and verification of conditions for induction of neutrophil extracellular traps in vitro].

This study aims to optimize the conditions for the formation of neutrophil extracellular traps(NETs) in vitro, so as to establish a relatively stable experimental research platform. Different conditions were compared, including commonly used laboratory animals(rats and mice) and a variety of cell sources(bone marrow neutrophils and peripheral blood neutrophils separated by percoll density gradient centrifugation). Different inducers like lipopolysaccharide(LPS) and phorbol 12-myristate 13-acetate(PMA) were used for induction in vitro. Myeloperoxidase(MPO)/citrullinated histone H3(CitH3)/DAPI immunofluorescence and cell free DNA(cf-DNA) content determination were used for comprehensive evaluation to screen the optimal conditions for the formation of NETs induced in vitro. Furthermore, the stability of the selected conditions for inducing the formation of NETs in vitro was evaluated by tetramethylpyrazine(TMP), an active component in Chinese herbal medicines. The results showed that coated poly-D-lysine(PDL) induced the formation of NETs in bone marrow neutrophils of mice to a certain extent. Both LPS and PMA significantly up-regulated the protein levels of MPO and CitH3 in mouse bone marrow neutrophils and elevated the cfDNA level in the supernatant of rat peripheral blood neutrophils. The cfDNA level in the PMA-induced group increased more significantly than that in the LPS-induced group(P<0.05). The results of immunofluorescence staining showed that the expression of MPO and CitH3 in mouse bone marrow neutrophils, rat bone marrow neutrophils, and rat peripheral blood neutrophils were significantly increased after PMA induction, especially in rat peripheral blood neutrophils. TMP significantly down-regulated the protein levels of MPO, CitH3, and neutrophil elastase(NE) in rat peripheral blood neutrophils induced by PMA. In conclusion, treating the peripheral blood neutrophils of rats with PMA is the optimal condition for inducing the formation of NETs in vitro. This study provides an optimal platform for in vitro studies based on NETs and a basis for studying the effects of traditional Chinese medicines targeting NETs.

Composition and Function of Neutrophil Extracellular Traps.

Neutrophil extracellular traps (NETs) are intricate fibrous structures released by neutrophils in response to specific stimuli. These structures are composed of depolymerized chromatin adorned with histones, granule proteins, and cytosolic proteins. NETs are formed via two distinct pathways known as suicidal NETosis, which involves NADPH oxidase (NOX), and vital NETosis, which is independent of NOX. Certain proteins found within NETs exhibit strong cytotoxic effects against both pathogens and nearby host cells. While NETs play a defensive role against pathogens, they can also contribute to tissue damage and worsen inflammation. Despite extensive research on the pathophysiological role of NETs, less attention has been paid to their components, which form a unique structure containing various proteins that have significant implications in a wide range of diseases. This review aims to elucidate the components of NETs and provide an overview of their impact on host defense against invasive pathogens, autoimmune diseases, and cancer.

Leukotriene B4-induced neutrophil extracellular traps impede the clearance of Pneumocystis.

Pneumocystis pneumonia (PCP) is a fungal pulmonary disease with high mortality in immunocompromised patients. Neutrophils are essential in defending against fungal infections; however, their role in PCP is controversial. Here we aim to investigate the effects of neutrophil extracellular traps (NETs) on Pneumocystis clearance and lung injury using a mouse model of PCP. Intriguingly, although neutrophils play a fundamental role in defending against fungal infections, NETs failed to eliminate Pneumocystis, but instead impaired the killing of Pneumocystis. Mechanically, Pneumocystis triggered Leukotriene B4 (LTB4)-dependent neutrophil swarming, leading to agglutinative NET formation. Blocking Leukotriene B4 with its receptor antagonist Etalocib significantly reduced the accumulation and NET release of neutrophils in vitro and in vivo, enhanced the killing ability of neutrophils against Pneumocystis, and alleviated lung injury in PCP mice. This study identifies the deleterious role of agglutinative NETs in Pneumocystis infection and reveals a new way to prevent NET formation, which provides new insights into the pathogenesis of PCP.

Identification of CCL20 as a prognostic predictor for severe fever with thrombocytopenia syndrome based on plasma proteomics.

BACKGROUND: Severe fever with thrombocytopenia syndrome (SFTS), a lethal tick-borne hemorrhagic fever, prompted our investigation into prognostic predictors and potential drug targets using plasma Olink Proteomics. METHODS: Employing the Olink assay, we analyzed 184 plasma proteins in 30 survivors and 8 non-survivors of SFTS. Validation was performed in a cohort of 154 SFTS patients using enzyme-linked immunosorbent assay. We utilized the Drug Gene Interaction database to identify protein-drug interactions. RESULTS: Non-survivors exhibited 110 differentially expressed proteins (DEPs) compared to survivors, with functional enrichment in the cell chemotaxis-related pathway. Thirteen DEPs, including C-C motif chemokine 20 (CCL20), calcitonin gene-related peptide alpha and Pleiotrophin, were associated with multiple organ dysfunction syndrome. CCL20 emerged as the top predictor of death, demonstrating an area under the curve of 1 (P = .0004) and 0.9033 (P < .0001) in the discovery and validation cohort, respectively. Patients with CCL20 levels exceeding 45.74 pg/mL exhibited a fatality rate of 45.65%, while no deaths occurred in those with lower CCL20 levels. Furthermore, we identified 202 FDA-approved drugs targeting 37 death-related plasma proteins. CONCLUSIONS: Distinct plasma proteomic profiles characterize SFTS patients with different outcomes, with CCL20 emerging as a novel, sensitive, accurate, and specific biomarker for predicting SFTS prognosis.